This invention relates to sputtering devices which deposit a metallic film on the surface of a workpiece by the utilization of a cathode sputtering phenomenon which occurs in a glow discharge.
In general, in sputtering devices, the cathode sputtering phenomenon accompanying glow discharge, that is, the phenomenon that the material of a cathode is vaporized into metallic atoms or a mass of metallic atoms by the bombardment of gas ions thereto, a part of the atoms being scattered, is utilized. The metallic atoms thus scattered are adhered to the surface of a workpiece positioned in the vicinity of the anode thereby to form a metallic film thereon.
A feature of such sputtering is that the lower the pressure of the gas atmosphere in which the sputtering is effected, the smaller the number of chances for the metallic atoms emitted from the cathode to collide with the residual molecules between the electrodes is, and at the same time the finer the finish of a metallic film obtained by depositing the metallic atoms arriving directly at the workpiece is. That is, the pressure of the gas atmosphere should be as low as possible to improve the quality of the metallic film deposited on the work piece.
In conventional sputtering devices of this type, conditions for effectively conducting sputtering in a glow discharge are experimentally determined by the nature and state of the gas and the cathode material employed therein, and especially the pressure of the gas, which must be maintained at a certain value (of the order of 1-2.times.10.sup.-2 Torr in direct current glow discharge, in general) for the occurrence of a glow discharge. Thus, lowering the pressure of the gas is limited.
Furthermore, in conventional sputtering devices, electrons emitted from the target during the sputtering collide with the anode thereby increasing the temperature of the latter. The temperature of the workpiece placed near the anode is also increased by the radiant heat from the anode. Therefore, the heat stability of the workpiece must be taken into consideration.